This invention relates to an improved intake system for a multiple valve type engine and more particularly to an improved induction arrangement that provides good running throughout the engine speed and load ranges and which ensures against the accumulation of unnecessary combustion deposits in the induction passages. In addition, the invention relates to an improved spark plug arrangement for such an engine.
It has been proposed to improve the output of an internal combustion engine by providing at least a pair of separate intake passages that deliver the intake charge to the combustion chambers of the engine. In order to ensure good running at low speeds, it has been proposed to employ a throttle valve arrangement in one of the induction passages that is operated in sequence with the main throttle valve so that the idle and low load charge requirements are supplied through only one of the intake passages. In this way higher velocities of induction are possible so as to improve the running under these conditions. However, the remaining induction passage is generally stagnant during such running even though the associated intake valve with it opens and closes. As a result, it is possible that combustion deposits such as carbon may accumulate in the non-utilized intake passage. In addition, since there is no flow of intake air across this intake valve, it may not be cooled sufficiently and cause overheating and/or early wear.
It is, therefore, a principal object of this invention so as to provide an improved induction system for an internal combustion engine.
It is another object of the invention to provide an induction system for an internal combustion engine embodying plural intake passages wherein good running is achieved throughout the engine speed and load ranges without detrimental effects in the induction system.
Engines embodying multiple intake passages and throttle valves for controlling the flow so that only one of the intake passages serves the major portion of the charge requirements at low loads may have different flow conditions existing within the combustion chamber when different numbers of the intake passages are serving the chambers. That is, when only one of the intake passages is serving the chamber, a swirling pattern may be established in the combustion chamber. When both passages, however, are supplying the charge, either a non-swirling pattern may be established or a flow path in a completely different direction may exist. Thus, if only a single spark plug is employed in the combustion chamber, this plug may not be positioned at the optimum location to fire the charge under all running conditions.
It is, therefore, a further object of this invention to provide an improved combustion chamber and spark plug location for a multiple intake passage internal combustion engine.